add some missing function listed in section 6.2. Numbers

README.md

@@ -63,7 +63,7 @@
 | 6.2.3 Implementation restrictions | yes | |
 | 6.2.4 Implementation extensions | yes | |
 | 6.2.5 Syntax of numerical constants | yes | |
-| 6.2.6 Numerical operations | yes | some functions that return multiple values are not supported for now. Also, picrin does not provide complex library procedures. |
+| 6.2.6 Numerical operations | yes | `denominator`, `numerator`, and `rationalize` are not supported for now. Also, picrin does not provide complex library procedures. |
 | 6.2.7 Numerical input and output | no | |
 | 6.3 Booleans | yes | |
 | 6.4 Pairs and lists | yes | |

piclib/built-in.scm

@@ -272,6 +272,20 @@
 				   (car (cddr x))))
 			     bindings))))))
 
+;;; 6.2. Numbers
+
+(define (floor/ n m)
+  (values (floor-quotient n m)
+	  (floor-remainder n m)))
+
+(define (truncate/ n m)
+  (values (truncate-quotient n m)
+	  (truncate-remainder n m)))
+
+(define (exact-integer-sqrt k)
+  (let ((n (exact (sqrt k))))
+    (values n (- k (square n)))))
+
 (define (boolean=? . objs)
   (define (every pred list)
     (if (null? list)